CN107107476B

CN107107476B - Joining objects together

Info

Publication number: CN107107476B
Application number: CN201580072239.2A
Authority: CN
Inventors: J·迈尔; M·莱曼; J·奎斯特; P·博世内尔
Original assignee: Woodwelding AG
Current assignee: Woodwelding AG
Priority date: 2014-11-04
Filing date: 2015-11-03
Publication date: 2021-05-11
Anticipated expiration: 2035-11-03
Also published as: WO2016071335A1; US20200316873A1; AU2015341864B2; JP2018501978A; US10894370B2; KR102388985B1; US20170334147A1; US10668668B2; EP3215346A1; BR112017008716A2; BR112017008716B1; RU2017117934A; RU2017117934A3; JP6876605B2; CN107107476A; KR20170078821A; MX2017005764A; RU2702543C2; AU2015341864A1

Abstract

A method of bonding a second object (2) to a first object (1), the method comprising the steps of: -providing the first object (1), the first object (1) comprising a solid thermoplastic liquefiable material; -providing the second object (2), the second object (2) comprising a surface portion having an engagement structure (4,5) with an undercut (5), whereby the second object (2) can be brought into a form-fitting connection with the first object (1); -pressing the second object (2) against the first object (1) by means of a tool (7) in physical contact with a coupling-in structure (6) of the second object (2), while mechanical vibrations are coupled into the tool (7), -continuing the steps of pressing and coupling vibrations into the tool (7) until the flowing portion of the thermoplastic material of the first object (1) liquefies and flows into the joining structure of the second object (2), -resolidifying the thermoplastic material of the first object (1) to produce a form-fitting connection between the first object (1) and the second object (2) by mutually infiltrating the joining structure (4,5) by the liquefied and resolidified flowing portion.

Description

Joining objects together

Technical Field

The present invention relates to the field of mechanical engineering and construction, in particular mechanical construction such as automotive engineering, aircraft construction, shipbuilding, machine construction, toy construction, etc.

Background

In the automotive, aerospace and other industries, steel structures tend to be abandoned in favor of lightweight materials such as aluminum or magnesium metal sheets or polymers, such as carbon fiber reinforced polymers or glass fiber reinforced polymers or polymers without reinforcing materials, such as polyesters, polycarbonates and the like.

These new materials pose new challenges in bonding elements of these materials, particularly in bonding a flat object to another object.

To address these challenges, the automotive, aerospace, and other industries have begun to use a large number of adhesive bonds. Adhesive bonds can be light and strong but have the disadvantage that the reliability cannot be controlled over a long period of time, since it is almost impossible to detect a weakened adhesive bond, for example due to a brittle adhesive, without completely destroying the bond.

FR1519111 teaches a method of fastening a screw or similar fixing element to a thermoplastic body by applying high frequency vibrations to the thermoplastic body to displace and flow a thermoplastic substance in an inner cavity of the fixing element. US5,271,785, FR2,112,523, US3,184,353, US3,654,688 and GB1,180,383 teach fixing a metal body to a thermoplastic body by bringing the metal body and the thermoplastic body into contact and subjecting the metal body to mechanical vibrations until the thermoplastic material of the thermoplastic body liquefies, the metal body is substantially completely encased in the thermoplastic body, and the thermoplastic material flows into recesses of the metal body. All these methods are only suitable for anchoring metal parts in deep thermoplastic objects and the energy input required and the corresponding influence of the parts to be connected are considerable.

US2010/0079910 teaches manufacturing an electronic device having a plastic housing part and a metal housing part, wherein the plastic housing part is attached to the metal housing part by ultrasonic bonding. The application of the concept taught by US2010/0079910 is limited.

Other concepts of prior art methods include shaping a thermoplastic body to include a flange-like protrusion into which a fastening element (such as a nut) is pressed. However, this concept has the disadvantage of being more complex, since the shaped plastic part may have a simple sheet form, for example with flanges, which, depending on the application, requires a precisely defined positioning, which may considerably increase the manufacturing costs.

Disclosure of Invention

It is an object of the present invention to provide a method of bonding two objects together which overcomes the disadvantages of the prior art methods and which is particularly suitable for bonding a second object to a first object of a polymer-based material. Another object is to provide an apparatus for carrying out the method.

According to one aspect of the invention, a method of bonding a second object to a first object, the method comprising the steps of:

-providing a first object comprising a thermoplastic liquefiable material in a solid state;

-providing a second object comprising a surface portion having an engagement structure with an undercut, and/or wherein the second object, as described below, the surface portion is deformable to comprise such an engagement structure with an undercut, whereby the second object can be brought into a form-fitting connection with the first object;

pressing the second object against the first object by means of a tool, which is in physical contact with the coupling-in structure of the second object, while mechanical vibrations are coupled into the tool,

-continuing the steps of pressing and coupling vibrations into the tool until the flowing portion of the thermoplastic material of the first object liquefies and flows into the joining structure of the second object,

-resolidifying the thermoplastic material of the first object to produce a form-fitting connection between the first and second object by the liquefied and resolidified flow portion and the flow portion of the joint structure interpenetrating.

The liquefaction of the flow portion is caused here primarily by friction between the vibrating second object and the surface of the first object, which friction heats the surface layer of the first object.

Thus, the special property of the method according to many embodiments of the invention is also that the already generated flow portion in the contact area between the first and second object can immediately flow into the existing cavity of the second object, and thus the area affected by the heat generated in the process is still small, e.g. essentially limited to the mixing zone.

The flow behavior of the flow section will be influenced by the fact that: thanks to the method according to the invention, a material flow (i.e. the second object; confluence) is generated towards the surface of the non-liquefiable material, to which surface heat is continuously supplied by vibration and friction. Therefore, generally, little heat flows away. Thus, even after short processing times, a large penetration depth of the thermoplastic material into the bonded structure can be achieved, the flow not being stopped by heat losses of the liquefied material in contact with the cold spot. This is in contrast to the "wood welding" (Woodwelding) process described in WO98/42988, for example, where there is a shunt in WO98/42988 as the liquefied material flows away from the interface region and thus transports heat to the structure which has been kept cold.

The first and second objects are structural components (structures) in a broad sense, for example components used in the field of mechanical engineering and construction, such as automotive engineering, aircraft construction, shipbuilding, machine construction, toy construction, etc. Typically, both the first and second objects will be man-made, artificial objects, and at least the first object will comprise man-made material; it is not excluded to additionally use naturally growing (non-biological) material, such as wood material, in the first and/or second object.

The material of the first and second objects may be uniform or non-uniform. For example, the first object may have a thermoplastic material, additionally comprising other non-liquefiable materials, and/or the first object may have multiple layers of thermoplastic material of different composition. Similarly, the second object may comprise different portions of different materials, as explained in more detail below. Additionally or alternatively, in embodiments, the second object may be caused to penetrate multiple objects (the first object plus at least one other object) to secure the multiple objects to one another, as also described in more detail below.

The coupling-in structure can be a coupling-in face, in particular constituted by the most proximal face, with or without a guide structure for a separate sonotrode acting as a tool (for example a guide hole for a corresponding protrusion of the tool). In an alternative embodiment, the coupling-in structure may comprise a coupling directly coupling the second object to the vibration generating device, which then acts as a tool. Such a coupling may be, for example, by means of a screw thread or a bayonet coupling or the like. Thus, in these embodiments, the second object is simultaneously an ultrasonic generator coupled to the vibration generating means.

In other embodiments, the tool is an ultrasonic generator secured to the vibration generating device. Such sonotrodes are known, for example, from ultrasonic welding.

In a further embodiment, the tool may be an intermediate piece (different from the first object) against which the sonotrode is pressed, and whose material does not liquefy under the conditions of application in the process. In general, methods according to aspects of the invention preclude coupling vibrations into the second object via only the first object; but rather requires physical contact between the second object and the vibrating tool.

The flowing portion of thermoplastic material is the portion of thermoplastic material that is liquefied and flows in the process and due to the influence of mechanical vibrations.

The bonding structure of the second object is a non-liquefiable material. As explained in more detail below, this definition includes the possibility that the material is liquefiable at a significantly higher temperature than the material of the first object, for example a temperature at least 50 ° higher. Additionally or alternatively, the condition may be maintained such that the viscosity of the material of the second object is several orders of magnitude higher than the viscosity of the thermoplastic material of the first object, for example at least 10, at a temperature at which the thermoplastic material of the first object is flowable³And 10⁵Coefficient of (d) between. Additionally or alternatively, different liquefiable matrix materials having different liquefaction temperatures and/or different glass transition temperatures are included, which can also be achieved by a higher filling level of, for example, fibrous fillers.

The engagement structure may comprise continuous radial projections and recesses (e.g. ribs/grooves), an open porous foam-like structure, a distally open opening defining an undercut by widening proximally at least one transverse direction, etc. Any structure defining an undercut with respect to the axial direction is suitable.

In a joint structure comprising continuous radial projections and recesses (e.g., around the outer surface of a portion of the second object or along the inner surface of the second object), the depth of the mixing zone may be defined as the radial depth of penetration of the flow portion from the outermost projection. In a bonded structure comprising an open porous structure, the depth of the mixing zone may be defined as the depth at which the thermoplastic material penetrates into the open porous structure starting from the surface of the open porous structure, the depth being measured perpendicular to the surface of the open porous structure. Similarly, in a joining structure comprising a distally-facing opening, the depth of the mixing zone may be defined as the depth at which the thermoplastic material penetrates from the distally-facing surface.

In particular, in an embodiment, the mechanical vibration transmission member of the second object consists of metal and/or other hard materials (glass, ceramics, etc.) and/or thermoset plastics and/or thermoplastics that remain below their glass transition temperature throughout the process.

In a particular set of embodiments, the second object comprises a second thermoplastic material having a liquefaction temperature substantially higher than the liquefaction temperature of the thermoplastic material of the first object. Then, after the step of liquefying the flowing portion of the thermoplastic material of the first object, the second object may be pressed against the support or the non-liquefiable portion of the first object while continuously coupling vibrations into the second object (with the same or higher or even lower strength as originally) until the second flowing portion of the second thermoplastic material is liquefied and causes the second object to deform. In particular, further method steps may be performed as described in WO2015/117253, which is incorporated herein by reference, until a foot and/or head of the second object is produced in order to join the first and second objects together by an additional rivet effect.

Although embodiments of this particular set of embodiments include a second object that passes through the first object to the far side after the bonding process, in an alternative set of embodiments, the far side remains intact, i.e., the mixing zone including portions of the first and second objects does not reach the far side.

In an embodiment, the second object is anchored in a depth-efficient manner by providing the second object with an anchoring portion, wherein the anchoring portion extends along an anchoring axis, optionally providing a structural member arranged on an outer circumferential surface of the second object and/or along an inner surface of an axially extending portion of the second object.

In an embodiment, in particular the penetration depth of the second object into the first object, i.e. the axial extension of those parts of the second object that penetrate into the first object, is larger (e.g. significantly larger) than the depth of the mixing zone, i.e. the area where both parts of the first and second object are present after the bonding process. In other words, in these embodiments including a depth-effective anchoring, the width of a portion of the second object that penetrates into the first object in at least one lateral dimension, and typically in both lateral dimensions, is less than the penetration depth of the second object into the first object. The depth of the mixing zone is then defined as the characteristic depth of the structural elements on the peripheral surface, i.e. the depth measured perpendicular to the anchoring axis.

Additionally or alternatively to including a depth-effective anchoring, one set of embodiments includes a bonding surface having a plurality of structural elements that are laterally spaced from one another and/or that may form an extended, e.g., circumferential, groove that conforms to a surface portion of the first object. For example, if the first object is planar, the structural element will extend along the plane.

Embodiments, for example including a depth-effective anchoring, may include providing a hole in the first object prior to the pressing step, and pressing a portion of the second object into the hole during the pressing step. The diameter of the bore is preferably selected to be smaller than the outer diameter of the part pressed into the bore. Such holes may be blind holes or through holes. But may also be anchored in other recesses such as grooves or the like.

Through holes may also be advantageous in embodiments where the second object is rather thin, e.g. a thermoplastic sheet. The method of bonding the second object to the first object may then comprise lining the through hole with the second object, for example for the purpose of fastening a further object thereto, to serve as a guide hole, to serve as a barrier which is only criss-crossing under predetermined conditions (as in the case of a spacer or a second object with a detachable cover or the like), or to have other purposes. In embodiments of this particular class, the thickness of the first object may correspond to 2-40 times or 2-20 times the depth of the interpenetration (depth of the mixing zone), in particular between 3 and 10 times.

According to another set of embodiments, the bonding is performed as a "planar bonding" or "flat bonding", which has a relatively small penetration depth. This set of embodiments may be particularly suitable for bonding a second object to a first object that is relatively thin or sensitive to damage, or that has the following high requirements: leaving the surfaces other than the surface to which the second object is bonded intact.

In this group of embodiments, the second object comprises a plurality of structures for inflow of liquefied material, wherein the plurality of structures are laterally spaced from each other, i.e. extend along a plane which during anchoring is parallel to a surface plane of the first object, or may, as the case may be, extend along another non-planar surface of the first object. In particular, the bond between the first and second objects may be a planar bond, wherein the interfacial region between the first and second objects is substantially parallel to the surface plane of the first object and is significantly larger than the penetration depth, e.g. at least 2 or 3 times, at least 5 times or at least 10 times larger in at least one dimension, preferably in both dimensions. Here, the penetration depth may be equal to the depth of the mixing zone or may be less than the depth of the mixing zone.

Embodiments that include bonding with a small penetration depth compared to the depth of the mixing zone may also include bonding a second object to a non-planar surface portion of the first object. For example, a first object may have a certain proximally facing surface contour and a second object may have an overall shape that conforms to the contour, or may be deformable to do so.

Alternatively, the first object may have a countersink or opening or an opening provided with another structure along its circumference, wherein the second object has a correspondingly adapted (e.g. conical if the opening is a countersink) shape. In embodiments where the first object is rather thin and requires a distal surface, the structural elements of the second object may be adapted to the depth in such embodiments. In particular, the relative dimensions of the structural elements may decrease distally such that their ability to accommodate flowable material decreases distally, and so does the thermal shock.

In an embodiment, the design criterion is that the volume of the structural element (e.g. recess or hole) into which the liquefied material can flow is larger than the displacement volume. This leads to the criteria of embodiments of the invention according to which the porosity along the surface portion comprising the joining structure is at least 50% at a certain depth. Porosity is defined herein as the fraction of the total volume occupied by empty space measured from the outer convex hull to a certain depth (corresponding to the depth of the mixing zone measured in the axial direction); it may also be applicable to macrostructures that are not necessarily considered "pores". If this alternative design criterion is fulfilled, it is not necessary to displace the volume to a surface or side or the like.

More generally, in embodiments, the method may include flowing the flow portion into the recess and/or aperture and preventing the flow portion from flowing to a lateral region of the second object.

To this end, the method may optionally comprise pressing a (non-vibrating) holding means against a proximal surface of the first object in the vicinity of the second object, e.g. around the interface between the first and second object, in addition to providing a depression/aperture volume satisfying the above conditions. Such a holding device may prevent a bulge or the like around the position where the second object is anchored in the first object.

In this set of "planar bonding" or other "planar bonding" anchoring embodiments, the second object comprises, in addition to the lumen (recess/hole), a distally protruding structure that may, for example, serve as an energy director. In particular, such distal protruding structures may have a shape with a distally tapering portion, e.g. terminating in a tip or edge or a rounded distal end. In this case, the lateral distance between the distal protruding structure and the lumen housing the flow portion may be minimal. In particular, any spacing between such distal protruding structures and the cavity may be avoided such that the overall shape of the second object at the distal surface undulates between the distal protrusion and the cavity.

In all the sets of embodiments described above, the engagement structure comprising undercuts with respect to the axial (proximal-distal) direction and thus making a form-fitting connection possible is a prefabricated property of the second object.

Additionally or alternatively, the second object may comprise a deformable portion, and the method may comprise forming the structure for a form-fit connection during pressing of the second object against the first object, while the mechanical vibration is coupled to the second object.

For example, the second object may comprise a plurality of deformable legs or deformable flanges extending as deformable structures in a substantially axial direction. During this process, the deformable structure bends away from the axial direction, such that an undercut is formed after resolidification.

Embodiments using this principle of deformation may have the advantage that the effective anchoring area may be larger due to the deformation than the portion of the surface area of the first object that is penetrated by the second object, i.e. the area may be increased compared to embodiments without deformation.

Another possible advantage is that, for example, lightweight deformable materials may be used for the deformable portion. In particular, materials may be used which are deformable at the temperatures at which the process takes place, but which exhibit a significant stiffness at room temperature (or more generally, the temperature at which the assembly will be used). For example, the deformable portion may be a thermoplastic material having a glass transition temperature significantly higher than the glass transition temperature of the thermoplastic material of the first body forming the flow portion.

In a specific embodiment with this principle PBT (polybutylene terephthalate) is used as the first body thermoplastic material, which becomes flowable at a temperature of about 180 ℃, and PEEK is used as the material of that part of the second body comprising the deformable portion. PEEK is not liquid/flowable at 180 ℃, but 180 ℃ is above its glass transition temperature (about 140 ℃).

More generally, in embodiments where the deformable portion comprises a thermoplastic material, it may be advantageous if the glass transition temperature of the deformable portion is between the glass transition temperature of the thermoplastic material of the first body and the temperature at which the thermoplastic material becomes sufficiently flowable.

In this context, the liquefaction temperature or temperature at which a thermoplastic material becomes flowable is considered to be the melting temperature of the crystalline polymer, whereas for amorphous thermoplastics the temperature at which an amorphous thermoplastic above the glass transition temperature becomes sufficiently flowable is sometimes referred to as the "flow temperature" (sometimes defined as the lowest temperature at which extrusion is possible), e.g. the viscosity drops below 10⁴pa s (in the examples, in particular substantially free of fibre-reinforced polymer, lower than 10³pa*s)。

In order to apply a reaction force to the pressing force, the first object may be placed against a support, e.g. a non-vibrating support. According to a first option, such a support may be opposite the facing bearing surface, i.e. distal to the site, against which the first object is pressed. This first option may be advantageous in that bonding may be performed without substantial deformation or even defects, even if the first object itself does not have sufficient stability to withstand the pressing force.

In embodiments that include deforming the second object during pressing of the second object against the first object, the support may include a shaping feature that assists in the deformation process. For example, the support may be shaped with shaped projections or shaped recesses to cause outward bending or inward bending, respectively, of the deformable structure.

It is also possible that the method uses the cooling effect of the support on the thermoplastic material of the first object, whereby the thermoplastic material of the first object is kept at a cooler temperature and thus more robust at the interface towards the support. Thus, the deformable structure will deform so as not to be too close to the interface of the support.

According to a second option, the far side of the first object may be exposed, e.g. by holding the first object along a side or the like. This second option has the following advantages: the distal surface will not be loaded and will remain unaffected if the second object does not reach the distal side.

In an embodiment, the first object is placed against the support without an elastic or yielding element between the support and the first object, such that the support rigidly supports the first object.

In one set of embodiments, the second object includes an inner portion and an outer portion with a gap therebetween. The engagement structure of the second object may then comprise an outer structure of the inner portion and/or an inner structure of the outer portion and/or an outer structure of the outer portion, and the step of causing the flow portion to flow comprises causing the flow to enter the gap.

Alternatively, the inner and outer portions may be formed together as a single piece.

In one set of embodiments, the second object includes a first portion of the first material and a second portion of the second material. This set of embodiments may for example save costs if the first part comprises critical sections (e.g. threads or other structures for connecting another element to the assembly of the first and second objects) which are made of high quality building materials, such as stainless steel, titanium, aluminium, copper etc., while the second part may comprise lower cost materials and mainly serves to stabilize the second object with respect to the first object.

In particular, if the second object comprises an inner portion and an outer portion, the inner portion may be a first material and the outer portion may be a second material. Therefore, by flowing the flow portion into the gap, the second object itself is stabilized in addition to being bonded to the first object.

Embodiments comprising a first portion of a first material and a second portion of a second material may for example comprise embodiments of the above group with deformable portions. In these embodiments, the deformable portion may for example belong to the second portion of the second material, and the mounting structure for mounting a further object to the first object or for other functions may be another non-deformable material, such as cemented carbide.

Another advantage of embodiments with first and second materials (in addition to optionally including deformable portions with the above-mentioned advantages) is that they provide the possibility of using lightweight and/or low-cost materials for those portions of the second object that consume much space (e.g. create a sufficiently large area in the above-mentioned sense) while maintaining the possibility of having a sufficiently stable/rigid functional piece, e.g. with a thread or other functional structure constituted by the first portion.

If the second material is itself capable of deforming and possibly of flowing at a temperature above the liquefaction temperature of the first object material, the method may have the further advantage that the first and second parts may optionally be assembled on site if they are not initially connected to each other or are only loosely connected. For example, the second material may flow relative to the first material to embed a portion of the first portion, e.g., in a form-fitting manner.

In one set of embodiments, the second object may constitute a mounting (mounting post, mounting plug, etc.) for mounting a further object to the first object. In particular, the inner part of the kind described above may comprise mounting structures such as screw threads or bayonet fitting structures or guide bushings or snap structures. The outer portion may serve as a fastening flange for fastening the mounting structure. This method has great advantages compared to the fastening flanges of the prior art:

instead of providing the fastening flange and mounting the fastening element to the fastening flange in two separate steps, the entire structure may be attached in one single step.

The positioning of the mount may optionally be performed directly on the otherwise finished first object, for example after the latter has been placed relative to the other part and/or for example in the presence of a further object. Thus, no precise alignment step is required during the manufacture of the first object itself. Therefore, the accuracy of positioning with respect to the final product may be drastically increased.

Thanks to the method according to the invention, the anchoring of the mounting structure is also effective in case the first object is rather thin and/or in case another distal surface of the first object needs to remain unaffected. This is in contrast to the prior art methods described above, which involve inserting a metal body (threaded bushing, etc.) into a thermoplastic object.

In particular, in an embodiment, the second object comprises a proximal body and has at its distal side a plurality of distal extensions which are pressed into the first object in the pressing step. In particular, the distal extension may comprise at least one outer extension and at least one inner extension.

For example, the proximal body may comprise a portion of the second material described above and have embedded therein a portion of the first material, which is also proximally accessible after the step of re-solidifying the thermoplastic material, and may have a mounting structure. The portion of the first material may extend distally to form at least one distal extension (e.g., a central protrusion) or may be constrained proximally.

In one set of embodiments, the first object is a flat object such as a polymer plate, e.g. a polymer cover.

The bond between the second object and the first object may have any purpose of bonding between the two objects. For example, in the automotive or aeronautical industry, the bond may be a bond between a structural element of plastic (first object) and a structural element of metal or composite material.

In one set of embodiments, the second object may be an anchor in the first object for securing additional elements thereto.

In another set of embodiments, the second object may be a connector that joins an additional third object to the first object by the methods described herein. Thus, these embodiments relate to:

a method of connecting a third object to a first object by bonding the second object to the first object and thereby securing the third object to the first object, the method comprising the steps of:

-providing a first object comprising a thermoplastic liquefied material in a solid state;

-providing a third object;

-providing a second object comprising a surface portion having an engagement structure with an undercut and/or such an engagement structure that can be deformed to comprise an undercut, whereby the second object can form a form-fitting connection with the first object;

-arranging a third object with respect to the first object,

-continuing the steps of pressing and coupling the vibrations into the tool until the flowing portion of the thermoplastic material of the first object liquefies and flows into the joining structure of the second object,

-causing the thermoplastic material of the first object to re-solidify to interpenetrate the joining structure by the liquefied and re-solidified flow portions to produce a form-fitting connection between the first and second objects,

-wherein the step of pressing the second object against the first object is performed until the second object is in physical contact with the third object and fixes the third object to the first object.

In particular, in the step of arranging the third object with respect to the first object, the third object may be placed on a proximal side of the first object, and after the step of arranging, the second object may be caused to penetrate the third object until a distal portion thereof reaches the first object to cause the second object to be pressed against the first object.

For example, to this end, the third object may be a liquefiable thermoplastic material or other permeable material such that the second object permeates through the third object until its distal portion reaches the first object.

Furthermore, it is also possible to arrange the joining structure of the second object in a form-fitting connection with a third object, in addition to the connection with the first object.

Additionally or alternatively, the third object may comprise a hole through which a distal portion of the third object is guided to reach the first object.

To secure the third object to the first object, the second object may include a head or bridge that rests on a proximally facing surface portion of the third object, while a distal portion of the second object is anchored in the first object.

Additionally or alternatively, if the third object comprises a thermoplastic material, the form-fit connection between the second object and the third object may also be caused by the material of the third object penetrating into the structure of the second object, in addition to the material of the first object which interpenetrates with the joining structure.

Additionally or alternatively, the thermoplastic material of the third object may be welded to the thermoplastic material of the first object by the action of the second object being pressed into the assembly of the third object and the first object, or the thermoplastic material of the third object may interpenetrate the flowable material of the first object in an immiscible manner to create a mechanical and/or adhesive connection after resolidification.

It may even be chosen to have the material of the third object bonded to the first object comprise an elastomeric material or other material, even if such a material is not liquefiable, and even if there is no pre-manufactured opening. In particular, the cutting portion of the second object may pierce a portion of the third object until contact is made with the first object placed distally thereof.

In this way (bonding of the soft material, which is infusible or meltable, to the thermoplastic first object) a connection between hard and soft materials (which cannot be processed together in hard/soft injection moulding, for example) becomes possible. One example is the combination of a damping pad (third object) with a thermoplastic first object such as a thermoplastic sheet.

In one set of embodiments, the second object comprises a structure at the surface that is in direct contact with the first object during pressing and vibration, which acts as an energy director, such as an edge or tip. For ultrasonic welding and the "wood welding" (Woodwelding) process described in WO98/42988 or WO 2008/080238, energy directors are known, which are usually present on the object of material to be liquefied. However, embodiments of the present invention reverse this by providing an energy director on the material that does not liquefy but which interpenetrates through the liquefied material.

The invention also relates to a connecting element for fixing to a first object comprising a thermoplastic material for use in the method described herein. More specifically, any property of the second object described and/or claimed with reference to the method may be a property of the connecting element, and vice versa.

In this context, the expression "thermoplastic material capable of being made to flow, for example by mechanical vibration" or simply "liquefiable thermoplastic material" or "liquefiable material" or "thermoplastic material" is used to describe a material comprising at least one thermoplastic component which becomes liquid (flowable) when heated, in particular when heated by friction, i.e. when arranged on one of a pair of surfaces (contact surfaces) which are in contact with each other and are vibrationally moved relative to each other, wherein the frequency of the vibrations has the above-mentioned characteristics. In some cases it may be advantageous for the material to have a coefficient of elasticity of more than 0.5GPa, for example if the first object itself has to carry a large amount of load. In other embodiments, the coefficient of elasticity may be lower than this value, because the vibration conducting properties of the first object thermoplastic material do not play a role in the process, because mechanical vibrations are directly transmitted to the second object by the tool.

Thermoplastic materials are well known in the automotive and aerospace industries. For the process according to the invention, thermoplastic materials which are particularly suitable for use in known applications in these industries can be used.

Thermoplastic materials suitable for use in the process according to the invention are solid at room temperature (or at the temperature at which the process is carried out). It preferably comprises a polymeric phase (in particular based on C, P, S or Si chains) which is converted from a solid to a liquid or is flowable above a critical temperature range, for example by melting, and when cooled again below the critical temperature range, for example by crystallization, wherein the viscosity of the solid phase is several orders of magnitude (at least three orders of magnitude) higher than that of the liquid phase. Thermoplastic materials will generally include a non-crosslinked covalently or crosslinked polymeric component, the crosslinking bond reversibly opening upon heating to or above the melting temperature range. The polymeric material may also include fillers, such as fibers or material particles, which have no thermoplastic properties or have thermoplastic properties that include a melting temperature range that is significantly higher than the melting temperature range of the basic polymer.

In this context, a "non-liquefied" material is generally a material that does not liquefy at the temperatures reached in the process, in particular at the temperatures at which the thermoplastic material of the first object liquefies. This does not exclude the possibility that the non-liquefied material is capable of liquefying at a temperature not reached in the process, which is typically higher than the liquefaction temperature of the thermoplastic material or the temperature at which the thermoplastic material is liquefied in the process (e.g. at least 80 ℃). The liquefaction temperature is the melting temperature of the crystalline polymer. For the amorphous stateThermoplastics, the liquefaction temperature (also referred to herein as the "melting temperature") is the temperature above the glass transition temperature at which it becomes sufficiently flowable, sometimes referred to as the "flow temperature" (sometimes referred to as the lowest temperature at which extrusion is possible), e.g., the viscosity of the thermoplastic material drops below 10⁴Pa s (in the examples, in particular substantially free of fibre-reinforced polymer, lower than 10³Pa · s).

For example, the non-liquefiable material may be a metal such as aluminium or steel, or wood, or a hard plastic such as a reinforced or unreinforced thermosetting polymer, or a reinforced or unreinforced thermoplastic having a melting temperature (and/or glass transition temperature) significantly higher than the melting temperature/glass transition temperature of the liquefiable portion, for example a melting temperature and/or glass transition temperature at least 50 ℃ or 80 ℃ higher.

Specific examples of thermoplastic materials are: polyetherketones (PEEK), polyesters, such as polybutylene terephthalate (PBT) or polyethylene terephthalate (PET), polyetherimides, polyamides, such as polyamide 12, polyamide 11, polyamide 6 or polyamide 66, polymethyl methacrylate (PMMA), polyoxymethylene or polycarbonate polyurethane, polycarbonate or polyester carbonate, or Acrylonitrile Butadiene Styrene (ABS), acrylate-styrene-acrylonitrile (ASA), styrene-acrylonitrile, polyvinyl chloride, polyethylene, polypropylene and polystyrene or copolymers or mixtures of these.

In embodiments where both the first and second objects comprise thermoplastic materials, the materials are selected such that the melting temperature of the material of the second object is significantly higher than the melting temperature of the material of the first object, for example at least 50 deg. higher. Suitable material pairs are for example polycarbonate or PBT for the first object and PEEK for the second object.

In addition to the thermoplastic polymer, the thermoplastic material may also contain suitable fillers, such as reinforcing fibers, for example glass and/or carbon fibers. The fibers may be staple fibers. Long or continuous fibers may be particularly useful for the portions of the first and/or second object that are not liquefied in the process.

The fibrous material, if any, may be a material known for fibre reinforcement, in particular carbon, glass, kevlar, ceramic, etc., mullite, silicon carbide or nitride, high strength polyethylene (Dyneema), etc.

Other fillers that do not have a fibrous shape are also possible, such as powder particles.

The mechanical vibrations or oscillations suitable for the method according to the invention preferably have a frequency between 2 and 200kHz (even more preferably 10 to 100kHz, or 20 to 40kHz) and a vibration energy of 0.2 to 20W per square millimetre of active surface. The vibrating tool (e.g. sonotrode) is for example designed such that its contact face oscillates mainly in the direction of the tool axis (longitudinal vibration) and the amplitude is between 1 and 100 μm, preferably in the range of 30 to 60 μm. Such preferred vibrations are generated, for example, by ultrasonic means known as ultrasonic welding.

In this context, the terms "proximal" and "distal" are used to refer to directions and positions, i.e., "proximal" is the side to which an operator or machine applies mechanical vibrations to couple, while distal is the opposite side. The proximal link expanse is referred to herein as the "head" and the distal expanse is the "foot". The "shaft" is the proximal and distal anchoring axis along which pressure is applied during the pressing step. In many embodiments, the mechanical vibration is a longitudinal vibration relative to the axis.

Drawings

Modes and embodiments for carrying out the present invention are described below with reference to the accompanying drawings. The figures are schematic. In the drawings, like reference characters designate the same or similar elements. Unless otherwise indicated, the figures show views of cross-section along a plane parallel to the anchoring axis (the "perpendicular" cross-section). The attached drawings show:

FIGS. 1a-1d illustrate a bonding process according to a first embodiment of the present invention;

FIG. 2 is an alternative configuration for the bonding engineering similar to the process of the first embodiment;

FIGS. 3a and 3b are bonding processes with an alternative second object;

FIG. 4a is a view from the far side of the second object;

FIG. 4b is a cross-section of a second object similar to FIG. 4 a;

FIG. 4c shows the second object of FIG. 4b anchored in the first object;

FIG. 4d is another variation of the second object;

FIGS. 5a and 5b are bonding processes with alternative first and second objects;

FIGS. 6a-6d are bonding processes according to yet another embodiment;

FIG. 7a is a hybrid second object for use in the process of FIGS. 6a-6 d;

FIG. 7b is a partial cross-section of another hybrid second object;

FIG. 7c is yet another partial cross-section of the second object of FIG. 7c after the process;

FIG. 7d is another hybrid second object that may be used in a bonding process without any foot formation;

fig. 8 and 9 are further embodiments of the second object;

FIG. 10 is another bonding process with an alternative second object;

FIGS. 11-16 are additional embodiments for bonding a second object to a flat first object;

FIGS. 17a-17b are bonding processes of a first object having a deformable portion and a first object;

FIGS. 18-20 are variations of this process;

FIGS. 21a and 21b illustrate the bonding of a third object to a first object by a second object;

FIGS. 22 and 23 are alternative second objects for this bonding process;

FIGS. 24a and 24b are top views of semi-finished products used to form yet another second object, and cross-sectional views of the second object formed thereby;

FIGS. 25 and 26 are views of yet another second object;

fig. 27 is a schematic horizontal section through a further second object;

fig. 28 is a bottom view of the cap member of such a second object;

FIGS. 29a and 29b are processes for bonding a foam material to a thermoplastic first object;

FIG. 30 is a further arrangement for bonding a second object to a first object;

fig. 31 is a modification of the second object;

FIG. 32 is a still further process of bonding a second object to a first object;

FIGS. 33, 34 and 35 are variations of this process;

FIG. 36 is a further second object for bonding to the first object; and

fig. 37 is a further second object for bonding to the first object.

Detailed Description

Fig. 1a depicts the basic setup of an embodiment of the present invention. The first body 1 consists of a thermoplastic material, such as for example a compact or foamed polybutylene terephthalate (PBT), or polycarbonate or acrylonitrile butadiene styrene or any other thermoplastic polymer that is solid at room temperature and has for example a melting temperature of less than 250 ℃.

The second object is for example a metal or a plastic (thermosetting or thermoplastic). If the second object is liquefiable, its liquefaction temperature is such that it is not flowable at the temperature at which the first thermoplastic material is flowable. For example, the second material has a melting temperature that is at least 50 ℃ or at least 80 ℃ higher than the melting temperature of the first material.

The second object has a structure which can be brought into a form-fitting connection with the material of the first object after the first object has flowed. More specifically, the second object has a surface portion with an undercut with respect to the axial direction (axis 10). For example, the surface structure comprises at least one rib 4 or at least one elevation extending in a non-axial direction. In the depicted embodiment, the second object is assumed to be rotationally symmetric about an axis 10 and comprises a plurality of circumferential ribs 4 with slots 5 formed therebetween.

At the distal end, the second object has a tip 3, and at the proximal end, a head 6 forms a proximally facing coupling surface for mechanical vibrations.

The ultrasonic generator 7 is used to press the second object against the first object while coupling mechanical vibrations into the second object. As shown in fig. 1b, liquefaction of the material of the first object starts from the interface of the tip 3. Continued pressing of the second object into the first object will cause the second object to move relative to the first object in the direction of the outlined arrow. A flow 11 of liquefied thermoplastic material of the first object occurs.

Fig. 1c shows the configuration at the end of the process. Since the first object is liquefied only near the surface of the second object, but will remain solid elsewhere and thus exhibit a certain rigidity, the liquefied material cannot spread arbitrarily, pressing the second object into the first object will generate a certain hydrostatic pressure on the first object, and this will result in the flow 11 immediately filling the undercut structures, such as the grooves 5.

After the vibration has stopped, the liquefied thermoplastic material will solidify again, so that the second object is firmly anchored in the first object (fig. 1 d).

FIG. 1d also shows the penetration depth d_pAnd the depth d of the mixing zone_i(depth of interpenetration), the latter being the depth of penetration of the flow portion from the outermost surface of the second object, where the depth d of the mixing zone_iCorresponding to the depth of the groove 5. As can be seen from fig. 1d, in these embodiments with a depth-effective anchoring, the penetration depth is substantially greater than the depth of the mixing zone.

Fig. 1d also shows the width w of the portion of the second object that penetrates into the first object. Obviously, this width is smaller than the penetration depth, which is also a further possible feature of embodiments of depth-effective anchoring.

The second object in this and other embodiments described herein may have the function of acting as a connector, guide hole (of a nut, bolt, etc.), bushing, other connector, etc.

In fig. 1a-1d it is assumed that the second object 2 is pushed through the surface of the first object 1 (similar considerations apply if a further third object is placed on top of the first object, as discussed in more detail below, e.g. with reference to fig. 21a/21 b; fig. 29a/29b, fig. 30). In the process, the volume of the anchoring portion (here: the shaft, i.e. the second object without the head 6) corresponding to the second object is displaced, for example, in the proximal direction and/or the introduction of the second object results in a slight deformation of the entire first object.

In the following cases:

such displacement and/or deformation is undesirable and kept to a minimum, and/or

-it is difficult to push the second object through the surface of the first object due to the shape/size of the second object and/or the resistance of the first object, and/or

It is difficult to guide the second object during introduction only by means of the sonotrode and/or external means,

optionally, the first object having the aperture 20 is provided prior to the step of pressing the second object against the first object. This is again schematically illustrated in fig. 2.

Diameter d for hole_hThe following considerations may be made (not only for the shape as shown in fig. 2, but generally for the portion of the second object that is pressed into the hole in the process):

diameter d of the hole_hShould be smaller than the outer diameter d of the protruding structure (ribs 5 in the shown embodiment) of the anchoring portion of the second object₂. An exception to this principle is conceivable for non-circumferentially symmetrical shapes.

In most embodiments, the diameter d of the hole should be chosen such that_hSuch that the volume of the hole is equal to or less than the volume occupied by the anchoring portion. In other words, the hole diameter in these embodiments should be selected such that the volume of the displaced portion of the first object thermoplastic material is approximately equal to or greater than the volume of the structure into which the displaced volume can flow. However, particularly in embodiments in which the engagement structure is defined by the open porous structure of the second object, it is not necessarily necessary that the flowable material flows into it against some resistance.

Diameter d of the pores according to requirements and material properties_hMay be selected to correspond substantially to the minor diameter d of the anchoring portion₁(where the smaller diameter corresponds to the diameter at the axial position of the groove, if defined)) Or less than the latter, or more than the latter (but not more than the outer diameter d)₂)。

In the various embodiments described herein, the distal tip 3 or edge and the edge of the rib or other protruding feature of the engagement structure act as an energy guide for liquefying the thermoplastic material.

The embodiments described herein show the sonotrode 7 (or "horn") as a separate part, which is pressed against the proximally facing coupling face of the second object.

However, especially in embodiments where the second object is a metal, the second object may be an ultrasonic generator directly coupled to the vibration generating device. For example, proximal screw threads or bayonet engaging structures or the like for fastening to corresponding coupling surfaces of the vibration generating device may be provided.

Although the embodiment of fig. 1a-2 is assumed to have rotational symmetry about axis 10, this is not a requirement. In contrast, it is even advantageous to provide in particular a structure which gives the anchoring portion a deviation from circumferential symmetry, as described below.

Fig. 3a and 3b also show an embodiment in which the second object 2 has an inner part 21 and an outer part 22 with a gap 23 in between. The engagement structure is defined along an exterior surface of the inner portion and/or an interior surface of the outer portion and/or an exterior surface of the outer portion. In the illustrated embodiment, the engagement structure (a plurality of circumferentially extending ribs defining grooves therebetween) is present only along the outer surface of the inner portion.

When the second object is pressed into the first object and the thermoplastic material of the first object is liquefied, the partially liquefied material flows into the gap (as flow 11 in fig. 3 b). In addition to anchoring the second object to the first object, the material will also stabilize the inner and outer portions relative to each other after the process is completed.

The following options apply:

the inner part and the outer part may be together in one piece, or they may be constituted by separate pieces, as shown in fig. 3a and 3 b.

In the latter case, they may optionally be made of different materials. For example, if the second object is a fastener for fastening something to the first object, the inner portion may be metal, while the outer portion may be a lighter, softer material, such as a plastic material having a higher melting temperature (liquefaction temperature) than the material of the first object. This includes the possibility that the material of the outer portion is a material whose liquefaction temperature is higher than its glass transition temperature of the material of the first object, so that it is deformable, which deformation contributes to the anchoring, as described above and explained in more detail below with reference to fig. 17A-20.

Omicron if the inner and outer portions are discrete, they may both reach the proximally facing coupling face, or only one of them reaches the coupling face as in the embodiment shown. In the depicted embodiment, the vibration is coupled to the inner portion via the outer portion.

Similar to fig. 2, holes may be made in the first object before the step of pressing the second object against the first object. Such holes may for example be used only for the inner part. Alternatively, it is also possible to manufacture the hole with an inner bore portion and, for example, a cylindrical outer bore portion for the corresponding portion of the second object.

The inner portion 21 and/or the outer portion 22 may be rotationally symmetrical about an axis (insertion axis/anchoring axis), or its structure may deviate from such symmetry.

The embodiment of fig. 3a and 3b may also have a hole in the first object, similar to the hole 20 shown in fig. 2. The hole diameter may be selected to suit the size of the core 21, according to the previous discussion of fig. 2.

Although the first and

second parts

21, 22 in the embodiment of fig. 3a/3b are shown as being pre-assembled, typically in embodiments where the two parts are not integral, the parts may be assembled on site, for example by the material of the first object connecting the parts and/or the material of the second part which has become deformable in the process or by other features.

In fig. 3a/3b, the parts are assembled before being anchored and the flow part fills the gap 23 between them, having the effect of creating additional stability of the bond between the

parts

21, 22.

For the gap between the inner part 21 and the outer part 22 there should be a minimum width of 0.1mm to enable the thermoplastic material to flow in.

Fig. 4a shows a view of an embodiment in which the second object has a metal inner part 21, e.g. of steel, and an outer part 22 of plastic, e.g. PEEK. The embodiment of fig. 4a has the following features that may be present together but may also be implemented alone or in combination:

the central portion has a tube section extending from the distal end (this includes the possibility that it is completely tubular).

The central portion includes internal threads 26 or other structures. If the tube section extends to the proximal end, the internal thread may also extend to the proximal end and may be used for mounting a further object to the second object after anchoring.

The engagement structure of the inner part is not rotationally symmetrical but comprises axial channels 24 which can guide the flow of material.

In an embodiment, such axial channel 24 is deeper than the circumferential groove 5 that causes the form-fitting connection, to act as a material distribution channel.

The outer portion 22 is not circularly symmetric, but comprises a plurality of outer axial projections terminating distally at an edge or tip.

The embodiment of fig. 4a is an example of an embodiment in which the second object forms a proximal object (or head) 29, from which the distal protrusion extends. The distal projection in the illustrated embodiment is formed by a leg extension 28 (outer projection) and a distal portion of the first part 21 (inner projection); circumferentially extending configurations, such as skirt-like external projections, are also possible.

In the above embodiments, the second object is anchored in a depth-efficient manner by providing it with an anchoring portion extending along the anchoring axis, and in some embodiments by means of a hole in the first object. These embodiments may have a plurality of structural elements (e.g. grooves 5) into which the liquefied material of the first object may flow, which structural elements are axially spaced apart from each other, for example arranged along a shaft and/or a tube or the like.

In the variant of fig. 4b, the metal inner part 21 and the plastic outer part 22 are preassembled. To increase the stability of the preassembly, the structure 4 of the inner portion 21 extends proximally into the area of the proximal body 29 and is cast into the material of the outer portion 22.

After the process of bonding the second object 2 to the first object 1, the effective height h of the proximal body 29 is higher than its initial physical axial extension, because the flowing portion of the thermoplastic material has filled the gap 23 between the inner and outer portions (reflow) (fig. 4 c). If the central opening is open distally as shown, some backflow will also occur in the central opening of the inner portion 21. If such backflow is to be prevented, the opening can be closed distally, for example by a pointed end element.

The post-process state as shown in fig. 4c illustrates well how the outer part 21 serves as a mounting for a further object, wherein the outer part 22 replaces the mounting flange of the prior art, wherein the outer part may be of a light, low-cost material and also adds considerable mechanical stability to the connection, in particular with respect to angular movements on the object fastened to the inner part 21 (on the thread 26).

If desired, additional stability with respect to axial forces can be provided if the outer part is provided with an inner structure (groove or the like) which is embedded by a flow portion of thermoplastic material to produce another form-fitting connection.

In the configuration shown in fig. 4b and 4c, the distal side of the inner portion 21 and the distal end of the protrusion 28 of the outer portion 22 are depicted as extending to substantially the same axial depth (the base lines are shown at equal heights). This is not a requirement. Instead, the axial extension of the inner projection formed by the inner portion 21 and the axial extension of the outer projection/projections can generally be selected independently of each other, according to requirements. For example, the inner portion 21 may extend further than the one or more projections 28 of the outer portion, or it may extend less far than the latter.

In a particular embodiment it does not even extend to the plane defined by the proximal surface in the assembled state (fig. 4c, the plane reaching the bottom of the arrow h) so that it is not pressed into the first object, but is only embedded in the flowable thermoplastic material that has flowed proximally due to the pressing force (backflow of the flowing portion).

Fig. 4d also shows a variant where the first (inner) part 221 does not reach the distal end of the second object. In contrast, the second portion 222 of plastic material comprises (two) at least one distal protrusion 28 and at least one inner (central) distal protrusion 27. As in the previous embodiments, the second object may be symmetrical with respect to a circle of rotation about the axis 10, or may have a discrete plurality of distal projections (as shown in fig. 4 a).

In contrast, the embodiment of fig. 5a and 5b is also suitable for anchoring a second object with respect to the first object if the first object is flat. To this end, the second object comprises a plurality of structural elements for the inflow of liquefied material, which are laterally spaced apart from one another, i.e. extend along a plane which is parallel to the surface plane of the first object during anchoring. At least some of the structural elements define undercuts.

In particular, in the embodiment of fig. 5a and 5b, the second object comprises a plurality of recesses 35 having, in cross-section, the shape of circular segments with a central angle greater than 180 °, so as to create undercuts. The recesses 35 may extend along a plane perpendicular to the plane of the drawing as grooves, or they may be present in other shapes and configurations.

As shown in fig. 5b, the step of pressing and coupling the vibration into the tool will result in liquefaction superficially starting at the interface between the first and second object, after which the liquefied thermoplastic material will flow into the recesses, thereby fastening the second object to the first object after re-solidification due to the undercut.

Another optional feature of this and other embodiments of the present invention is schematically illustrated in fig. 5 b. When the second object is pressed against the first object, a reaction force acts on the first object. In many embodiments, this reaction force will be exerted by a non-vibrating support on which the second object is placed, for example by a table or floor or a dedicated support. In some cases, such a non-vibrating support will be arranged such that a portion of the first object directly below the second object (more generally, such that a portion of the first object extends distally from the interface between the first and second objects) is supported. But this is not necessarily so. In fig. 5b, the support structure 41 is located directly below the second object such that there is no support for the first object, i.e. the far side of the first object is exposed. This may be advantageous in case the distal surface of the first object has a well-defined shape or other properties that must not be affected by the bonding process.

The feature of exposing the distal surface of the first object facing outwards from the interface with the second object is independent of the other features described with reference to fig. 5b, i.e. may also be implemented in other embodiments, and the embodiments of fig. 5a and 5b may also be performed in an arrangement where the distal surface is supported.

In the embodiment of fig. 5a and 5b, the depth d of the mixing zone is exemplified by a planar integration_iIs greater than the penetration depth d of the second object into the first object_p. This illustrates well the fact that these embodiments are particularly suitable for bonding a second object to a flat first object or other object that cannot be anchored deeply effectively. However, these embodiments also do not have the disadvantages of adhesive bonding described above.

The bonded width w of the mixing zone in the embodiment of planar bonding in at least one lateral dimension and typically in both lateral dimensions is significantly greater than the penetration depth, which is another possible feature of planar bonding.

The combined bonding process is also described with respect to fig. 6a-6 d. It is assumed that the second object 2 has a shape similar to the shape described with reference to fig. 1a-2, wherein the anchoring portion comprises a plurality of protrusions and recesses between the protrusions. The second object comprises a thermoplastic material having a liquefaction temperature substantially higher than the liquefaction temperature of the first object. For example, the second object may be made of PEEK, while the first object is made of PBT or polycarbonate.

The first object comprises a through hole 20 in which the second object is anchored.

To this end, in a first phase shown in fig. 6b, the second object is pressed against the first object while mechanical vibrations are coupled into it until the thermoplastic material of the first object starts to liquefy, so that the second object advances in the distal direction while the flow 11 of the thermoplastic material of the first object enters the recess 5 of the second element.

In this embodiment, the support 42 against which the first object is placed comprises a mould part forming a cavity 44 when the first object is placed against the support. The second object has an excess length such that at some stage of the process, the distal end of the anchoring portion abuts the support member 42 before the distally directed stop surface of the head 6 abuts the first object. Thereafter, further pressing force and mechanical vibration are applied and possibly intensified until the thermoplastic material of the second object 2 also becomes flowable (flow 51 in fig. 6 c) and fills the cavity. This will result in the second object being joined to the first object by means of the head 6 and the foot 52 by means of a further rivet effect (fig. 6 d).

In addition to contributing to the anchoring, the fact that the thermoplastic material of the first object has flowed into the structure of the second object also results in a sealing effect.

While in the embodiments of fig. 6a-6d and in other embodiments it is not essential that the first and second objects are assumed to be substantially uniform. Rather, the first and/or second objects may be mixed components of different materials. For illustrative purposes, fig. 7a depicts an embodiment in which a second object 2, comprising a metal portion 61 and a distal plastic portion 62 such as PEEK, is bonded to the first object, such as in the process described with reference to fig. 6a-6 d.

In the variant shown in fig. 7b, the distal plastic part 62 is a sheath element connected to the metal part 61 in a form-fitting manner. Fig. 7c shows the situation after the process, the deformed part of the plastic part 62 forming the foot 52, as described above.

The embodiment of the combined joining process with the additional rivet effect is also particularly suitable for joining a further object to a first object, the rivet-like connection consisting of a second object fixing the first and the further object to each other, as explained in more detail below with reference to the further embodiments.

Fig. 7d also shows a hybrid second object 2 with a metal part 61 and a plastic part 62, which may also be suitable as a connection in a process of the above-mentioned type, for example with reference to fig. 1a-1d or 2.

Fig. 8 shows a further embodiment of the second object 2. Similar to the two-piece embodiment as shown in fig. 3a and 3b, it comprises an inner part 21 and an outer part 22 between which the thermoplastic material of the first object can flow. More particularly, the inner portion 21 is shaft-like with an

outer structure

4,5 forming an undercut with respect to the axial direction. Additionally or alternatively, the outer portion 21 has an inwardly facing configuration, such as the illustrated groove 71 forming an undercut.

In the depicted embodiment, the second object is an integral piece forming the inner portion 21 and the outer portion 22. The gap 23 in the embodiment as in fig. 4a, 4b, 4, 8 can be seen as an opening open to the far side of the surrounding central protrusion 21.

Compared to an embodiment with only one pin-like shaft, an embodiment with an inner part and an outer part brings additional anchoring stability due to the interaction between the inner part and the outer part, especially if the thermoplastic material of the first object is rather soft or thin or brittle.

In the embodiment of fig. 9, the second object 2 comprises a body 73 of, for example, a solid metal material and an interpenetration member 74 of an open porous material, such as a metal foam or a metal mesh. The interpenetrating member is fixed to the solid metallic material. The main body 73 forms at least a part of the proximally facing coupling-in face and the interpenetration member 74 forms at least a part of the surface portion in contact with the first object. Due to the effect of the mechanical vibrations and the pressing force, the thermoplastic material penetrates into the interpenetration member 74 and this forms undercuts due to its open porous structure, thereby forming a joint structure.

The embodiment of fig. 10 is an example of an embodiment having an inwardly facing engagement structure. More specifically, the second object 2 has an undercut recess 35 into which the thermoplastic material penetrates. The outer distal tip or edge 3 serves as an energy director. The outer surface 75 of the second object also forms an engagement structure with the undercut with respect to the axial direction as the distal edge 3 is bent outwards. The embodiment of fig. 10 is an example of the principle described with reference to fig. 5a and 5b, where the depth of the mixing zone exceeds the penetration depth applied to the elements for point connection instead of flat connection.

Fig. 11 shows an alternative embodiment of a flat connection, in which the depth of the mixing zone exceeds the penetration depth. This embodiment is an example of an embodiment that optimizes a flat connection with the first object, wherein the influence of the connection is minimized, for example due to the need to maintain a certain quality of the surface portions (distal surface portions and/or proximally facing surface portions surrounding the second object) to which the second object 2 is not directly attached. The principle of bonding is based on undercut recesses 35, similar to that of fig. 5a/5 b. In the embodiment of fig. 11, the following measures are implemented:

the second object 2 comprises a protruding structure 36 with a distal edge or tip 3, which acts as an energy director and causes a rapid onset of liquefaction around the protruding structure.

The volume V1 of the protruding structure is less than or equal to the volume V2 of the recess (see fig. 12) into which the thermoplastic material can flow. The separation depth between the volumes V1, V2 (dashed line in fig. 12) is here defined as corresponding to the depth to which the second object is inserted into the first object, i.e. the dashed line corresponds to the level defined by the proximally facing surface of the first object. By this measure it is ensured that there is a space in the vicinity into which the thermoplastic material can flow for all parts displaced by the protruding part. Thus, the method has minimal material displacement and therefore minimal heat flow.

The recess and the projection are arranged next to each other. That is, there is no spacing e (fig. 13) between the protrusion 36 and the depression 36, or such spacing is minimal. Furthermore, by this measure, the material flow and thus the heat flow is minimized.

In the embodiment of fig. 11, the illustrated structure may extend cylindrically perpendicular to the plane of the drawing. Alternatively, the depressions or protrusions may be rounded or have other shapes that are limited in both lateral dimensions and arranged in a pattern of surfaces. For example, the second object may have a regular arrangement of dome-shaped (in particular spherical dome-shaped) recesses, each surrounded by ridge-shaped protrusions. Or the mountain shaped projections may be patterned with groove shaped depressions between them. Segmentation and other arrangements are also possible.

Fig. 11 also shows that the depth of the mixing zone is greater than the penetration depth, and that in the region of the bond with the second object, the effective thickness d is increased compared to the actual physical thickness d of the object_eff。

In the embodiment of fig. 11, anchoring requires a relatively large depth due to the tip or edge shaped protrusion. In an alternative configuration, a compromise between the energy directing action of the edge or tip and the requirement of a smaller depth may be made, for example by using a lobe 36 as shown in fig. 14.

Other cross-sectional shapes are possible, including the sharper shape shown in fig. 15. Such shapes may be easier to manufacture by methods such as cutting or milling, depending on the manufacturing method chosen. More generally, the manufacture of the first object may comprise a material removal method as well as a casting method, or as mentioned above, an open porous structure is used.

The energy impact and the required pressure are higher for a second object having a substantially flat distal end face 81 as shown in fig. 5a or also in fig. 16 compared to a second object 2 of the type shown in fig. 11, for example. Such objects are particularly suitable for anchoring in very thin first objects, such as organometallic sheet materials. The bonding is optimized to maximize the strength per penetration depth, while the effect of the bonding process of the first object is generally higher than in fig. 11 and other embodiments.

In the above-described embodiments, the engagement structure comprising undercuts with respect to the axial (proximal-distal) direction and thus making it possible to form a form-fit connection is a prefabricated property of the second object. Hereinafter, an embodiment in which such a form locking structure is formed by deformation in this process is described.

Fig. 17a depicts a basic embodiment of this principle. The second object 2 comprises a main portion 90 and a plurality of deformable legs extending distally from the main portion 90. The material of the second object may be such that plastic deformation of the leg portion and/or elastic deformation of the leg portion is possible. In an embodiment, the second object is made of metal, wherein the leg portions are sheet portions of sufficient thickness to be deformable under the conditions applied during bonding. Alternatively, the second object may be a polymer-based material with a suitably selected level of reinforcement, or any other suitable material or agglomerate.

Fig. 17b depicts the second object 2 anchored in the first object 1. The legs 91 are deformed to expand outward upon insertion under the impact of mechanical energy and pressing force, thereby creating a joint structure after resolidification.

Fig. 18 shows an embodiment of the principle of combining the embodiments of fig. 3a/b and 17 a/b. In addition to including an outer portion 22 having a deformable portion 91 (deformable leg or other deformable structure), the second object also includes an inner portion that is not deformable in the illustrated embodiment.

Fig. 18 also shows two other principles that can be implemented independently of the configuration of fig. 18.

First, the method in an embodiment further comprises pressing the holding means 93 against the proximal side of the first object in the vicinity of the second object, while the second object is bonded to the first object (in fig. 18, the holding means is shown on the left hand side only, but it may also completely surround the second object). Thereby, bulges or the like caused by pressing the second object into the first object are avoided (refer to fig. 1b/1 c).

Secondly, similar to the embodiments of fig. 5, 10, 11, etc., the process may be performed to cause backflow of material into the inner space of the second object, here the space between the inner and outer portions. Thus, the closest portion of the thermoplastic material that has flowed during the process is proximal to the initial proximal face. As described above, this backflow enhances the effective anchoring depth. In an embodiment, a retaining device 90 of the type described may assist in this process in that it maintains pressure around the second object, thereby allowing backflow within the interior space/cavity, rather than around it. The amount deltah shown in the figure shows the difference in the material that has flowed in with respect to the proximal face around the second object and may also correspond to an increased effective anchoring depth.

Fig. 19 shows an example of an embodiment in which the support 42 against which the assembly of the first and second objects is pressed by the sonotrode 7 has shaped features that help the deformable portion of the second object 2 to deform. More particularly, in the embodiment shown in fig. 19, the support 42 has shaped projections cooperating with corresponding recesses of the first object 1. The shaped projections are made of a material that is not liquefiable and does not soften in the process. Further, the support including the projections 46 or other shaped features may have a cooling effect such that the first object material remains hard at the interface therewith, e.g., due to being actively cooled. Thus, the deformable portion is guided to protrude from the shaped feature during deformation, as shown in fig. 19. More specifically, the deformable legs constituting the deformable portion are caused to bend outwardly away from the shaped projections 46.

Fig. 20 shows an alternative embodiment in which the shaped features include shaped recesses 44 such that the deformable legs are bent inwardly into the configuration shown in fig. 20. Various other alternatives are possible.

In general, the second object may have the purpose of being an anchor for another object to be attached to the first object, or it may itself be such second object, in the above figures the first object is shown without any functional structure for this purpose, however any such structure, e.g. a fastening structure or other functional structure, is possible.

Embodiments are described below in which a second object ("third object") is bonded to a first object during the bonding process by bonding the second object to the other object.

Fig. 21a depicts a basic configuration. The second object 2, which is used as a connector in the embodiment of joining a first object to another third object, is depicted similar to the connector of fig. 1a without a head. Alternatively, other shapes of the second object are possible; in particular all objects described herein, including second objects with heads, suitable for a deep effective anchoring may be used. The third object 100 is shown as a thermoplastic body, similar to the first object 1. It abuts against the proximal face of the first object 1. For coupling, the second object 2 is driven through both the third object 100 and the first object to be anchored in both the first and third objects, as shown in fig. 21 b.

The third object may comprise a thermoplastic material that can be welded to the thermoplastic material of the first object 1. For example, it may be a thermoplastic material with the same polymer matrix. In the area around the second object, welding may result, as indicated by the circle 101, due to the liquefaction caused in the process. More generally, the material of the third object in the process is pressed into the first object to facilitate the connection after resolidification. If welding is not possible because the materials of the first and third bodies cannot be mixed in the liquid state, this is still possible.

Additionally or as an alternative to the material being driven through the third object, the second object (connector) may also be driven through a preformed opening of the third object, so that its distal portion is anchored in the first object. Such a preformed opening may have a diameter that allows the second object to pass through substantially without resistance (see the embodiments described below), or may encounter substantial resistance there to enable mechanical energy to be absorbed.

Fig. 22 shows a modification of the second object 2. This variation differs from the previously described embodiment in that it has a compressed structure caused by the distally facing recess 111. This portion will cause the thermoplastic material of the third object 100 to be pressed into the first object 1, thereby creating a more pronounced mixing and, if applicable, a weld between the materials of the third object and the first object.

Fig. 23 shows another example of a second object 2 suitable as a connecting piece in the sense described. In particular, the second object 2 according to fig. 23 is particularly easy to manufacture and can be produced as a low-cost article. More specifically, the second object includes a sheet portion of, for example, metal. The tab portions form a plurality of legs 112 having barbs 113, all of which extend from and are integral with the bridge portion 114. The second object may be made from stamped sheet metal simply by bending the legs away from the bridge 114 and bending the legs 112 to have barbs 113.

Similarly, the embodiment of fig. 24a and 24b has a head 114 (or bridge) with a plurality of legs extending therefrom. Fig. 24a shows a punched metal sheet as an intermediate member, and fig. 24b shows a second object 2 obtained by deforming the intermediate member by bending. The legs may be provided with beads or grooves (as in fig. 23) for additional stability.

In this embodiment, instead of barbs, the legs 112 have distal arrow portions 115. Combinations are also possible.

Further, an optional feature independent of the legs consists of a central hole 116, which central hole 116 may be used for guidance during the assembly process, e.g. together with a flange 117. Other uses of such holes and/or flanges are possible, including fastening another object to a second object.

Fig. 25 shows a second object formed by a porous metal hollow cylinder 121. The perforations 122 of the metal cylinder can be interpenetrated by the thermoplastic material during the process, thus ensuring a form-fitting anchoring. To minimize proximal heating, the volumetric portion of the perforation may advantageously be close to or higher than 50%.

The second object of fig. 26 includes a metal mesh 125 also forming a hollow cylinder. The functional principle is similar to that of a hollow cylinder, wherein a mesh is used for the interpenetration of the thermoplastic material.

Instead of forming a hollow cylinder, a perforated metal sheet or mesh may form other shapes for constituting a connection piece of the type in question. Figure 27 shows very schematically a spiral shape as an option.

Other than cylindrical (fig. 25 and 26) and alternative where the material is a stable spiral, is corrugated, for example extending along the length dimension. The amplitude of such waves may be at least 5-10 times the thickness of the sheet or web.

Still further variations are square (cross-section perpendicular to the axial direction) or other closed or open shapes with bends or flexures.

The second object having the structure described with reference to fig. 22-27 and with reference to fig. 37 below may typically be very thin and therefore sensitive to buckling. To this end, the proximal connector structure may be advantageous to provide stability, depending on the application.

Fig. 28 shows a cap 141 with a groove 142 that acts as a proximal bridge for the second object 2 with a helical metal sheet or mesh to give the second object additional mechanical stability during the procedure.

A second object having a thin structure as described with reference to fig. 22-28 and with reference to fig. 37 below is also suitable for fixing in a relatively thin first object with a relatively small energy input. The volume displaced due to their thinness is very small and the melt zone will be very localized. This minimizes the total pressure and total energy input.

The second object 2, which is a connector of the type described with reference to fig. 22-28, may be particularly suitable for fastening first and third objects together in a pin-like or pin-like manner by the process described herein. In this context, the way in which the first and third objects are arranged relative to each other with respect to the proximal and distal anchoring axis may be varied, in particular, instead of the opposite way it is also possible to press the connecting element through the first object into the third object.

Fig. 29a and 29b show a particular application of the principle of connecting a third object 100 to a first object 1 using a connecting element. The second object is assumed to have a cap-like shape with a circumferentially protruding section 131 extending distally from the main body 132.

In this particular example, the third object 100 comprises a foam (compression part 102) that is compressed by the insertion of the second object 2. Optionally, the second object may include slack openings 133 or other shape features that allow the compressed material to flow away if the foam is thermoplastic (not necessary). Fig. 29b shows the corresponding outflow section 103.

While fig. 29a and 29b show the fastening of a third object of foam material, similarly, third objects of other materials, such as soft and/or elastic materials that can be penetrated by the distal structures of the second object or objects with preformed holes for these structures, may be fastened by this method.

In the embodiment of fig. 30, the third object 100 is provided with an aperture 109, through which aperture 109 a distal portion of the second object can be advanced to contact the first object. Herein, the third object 100 may be thermoplastic and the hole 109 may be undersized relative to the second object such that its insertion encounters resistance and the material of the third object surrounding the hole 109 is displaced. Alternatively, the third object may be a non-liquefiable material. The hole 109 then needs to be sized so that the distal portion of the second object fits through it or the distal tip or edge to penetrate the third object material.

The second object in the embodiment shown comprises resilient barb structures 118, the resilient barb structures 118 allowing the distal portion of the second object to be squeezed through the hole 109, but ensuring anchoring in the first object 1 after liquefaction and resolidification. The second object also has a proximal head 6 for fixing the third object 100 against the first object 1.

As an alternative to having resilient barb structures 118, a second object having a structure similar to that shown in fig. 30 may also have a shape similar to that of the structure in fig. 1a, also having a proximal head portion 6, for example as shown in fig. 31.

Fig. 32 depicts an embodiment in which a second object 2, e.g. entirely metal, is anchored in a through hole 20 of the first object. The through hole narrows distally (is a countersink) and the second object tapers accordingly to anchor around the hole. It is assumed that the first object 1 is a thermoplastic sheet.

The bond of the second object to the first object is a flat bond, similar to fig. 5a/5 b; fig. 11 and others teach that there are interpenetrating structures formed by sharp protruding structures 36 and depressions 35, although the bonding surface of the second object is not planar but conical.

Fig. 33 shows an alternative, in which the through hole 20 of the first object is not tapered but stepped, wherein the fastening surface comprises a protruding structure 36 and a recess 35 anchored around the step.

According to another alternative, as shown in fig. 34, if the second object 2 is allowed to protrude above the proximal surface of the sheet-like first object 1, the head-like proximal extension 6 of the second object may have a distal end

face comprising structures

35, 36 connecting the second object to the edge of the through hole.

In the variant of fig. 35, for other configurations similar to fig. 32, two optional further features are implemented (which can be implemented independently of one another, with advantages if they are combined):

the size of the

structural elements

35, 36 decreases distally,

the opening angle α of the second object's taper is larger than the opening angle β of the through-hole 20's taper, so that the second object penetrates more into the first object at a proximal location closer to the periphery than a distal location closer to the center.

Both measures have the effect that more energy is absorbed and more material is liquefied at more proximal peripheral positions than at more distal central positions around the opening. The effect is that the distal surface of the first object remains intact.

Fig. 36 shows a variant of the embodiment of fig. 11, but the structural elements in which the bonding is caused are limited to the periphery of the second object 2. In a more central position, the distal surface 151 acts as a stop and an abutment surface, defining precisely the axial relative position. Herein, consideration of fig. 12 with respect to the relative volumes of the projection arrangement 36 and the indentation 35 may be particularly advantageous.

Fig. 36 is thus a very schematic example of an embodiment in which the connection region between the first and second object constitutes only a part of their mutual interface. In other parts of the interface, there is essentially no energy transfer and no liquefaction takes place.

In the embodiment of fig. 37, a protruding structure 161 for anchoring in the second object is attached to the body of the second object and protrudes distally in a direction substantially parallel to the axial direction. The projection arrangement may for example be formed similar to the arrangement shown in fig. 23, 24b, 25 and 26 and is particularly simple and cost-effective to manufacture.

To be stable with respect to buckling, the metal plate or mesh may extend in a curved shape (e.g. by forming a cylinder) or a wave shape (perpendicular to the plane of the drawing) or other non-linear shape, as described above.

In one example, the body of the second object 2 may be a liquefiable material (liquefiable at the same temperature as the thermoplastic material of the first object, at a higher temperature, or even at a slightly lower temperature), into which the protruding structures 161 are cast. In an embodiment, the porosity of the structure may be at least 50%.

Claims

1. A method of bonding a second object to a first object, the method comprising the steps of:

-providing the first object, the first object comprising a liquefiable thermoplastic material in a solid state;

-providing the second object comprising a surface portion having an engagement structure with an undercut and/or being deformable to comprise such an engagement structure with an undercut, whereby the second object is capable of a form-fit connection with the first object;

-pressing the second object to the first object by means of a tool, which tool is in physical contact with the coupling-in structure of the second object while mechanical vibrations are coupled in to the tool,

-continuing the steps of pressing and coupling vibrations into the tool until the flowing portion of the thermoplastic material of the first object is liquefied and flows into the joining structure of the second object,

-resolidifying the thermoplastic material of the first object to produce a form-fitting connection between the first and second objects by the liquefied and resolidified flow portion being mutually permeable with the joining structure;

wherein the engagement structure comprises a plurality of laterally spaced openings that are distal to and each define an undercut relative to the axial direction, the flow portion comprising backflow into and undercut defined by the plurality of laterally spaced openings, wherein a distal portion of the plurality of laterally spaced openings is embedded in the first object during the method.

2. The method of claim 1, wherein the coupling-in structure comprises a proximally facing coupling-in face.

3. The method of claim 1, wherein the coupling-in structure comprises a structure for securing the second object to a vibration-producing device.

4. The method of claim 1, wherein the bonding structure of the second object is a material that is liquefiable or not liquefiable at a temperature substantially higher than the liquefaction temperature of the flow portion.

5. The method according to claim 1, wherein the second object comprises a second thermoplastic material having a liquefaction temperature significantly higher than the liquefaction temperature of the flow portion, the method comprising pressing the second object against a support and/or a non-liquefiable part of the first object after the step of liquefying the flow portion of thermoplastic material of the first object, while coupling vibrations into the second object until the second flow portion of the second thermoplastic material is liquefied and flows causing the second object to deform.

6. The method of claim 5, wherein the first object comprises a through hole, wherein the second object is pressed into the hole in the pressing step, and wherein the deforming of the second object comprises forming a foot as a widened distal end distal to the first object.

7. The method of claim 1, wherein the first object is provided with a hole and a portion of the second object is pressed into the hole in the pressing step.

8. The method of claim 7, wherein the aperture is selected such that the volume of the displaced portion of the flow portion is equal to the volume of the structure into which the displaced volume can flow.

9. The method of claim 1, wherein to apply the counter force, the first object is placed against a non-vibrating support.

10. The method of claim 9, wherein the support comprises a support surface facing a location against which the first object is pressed.

11. The method of any one of claims 1 to 9, wherein a distal side of the first object is exposed that is in face-to-face relation with a region against which the first object is pressed, the distal side being unsupported during the pressing step.

12. The method of claim 1, wherein the second object comprises a first portion of a first material and a second portion of a second material.

13. The method of claim 1, wherein the liquefaction temperature of the flow portion is 200 ℃ or less.

14. The method according to claim 1, wherein the second object has a deformable portion, the method comprising deforming the deformable portion by the step of pressing and coupling mechanical vibrations into the tool, while the deformable portion is at least partially surrounded by the liquefied material of the first object.

15. The method according to claim 14, wherein the second object comprises a head or bridge from which the deformable portion projects distally substantially parallel to a proximal-distal anchoring axis.

16. The method of claim 14 or 15, wherein deforming the deformable portion comprises bending the deformable portion away from an axial direction.

17. The method of claim 14 or 15, comprising placing the first object against a support during the pressing step, wherein the support has a shaped structure that assists the deforming.

18. The method of claim 1, securing a third object to the first object through the second object.

19. The method of claim 18, wherein the step of pressing the second object to the first object is performed until the second object is in physical contact with the third object and secures the third object to the first object.

20. The method according to claim 18 or 19, wherein the third object comprises a thermoplastic material and the flowing portion of the thermoplastic material of the third object flows relative to the second object by impact of pressure and mechanical vibration.

21. The method according to claim 18 or 19, wherein in the step of arranging the third object relative to the first object, the third object is placed proximal to the first object, and after the step of arranging, the second object is caused to penetrate the third object until its distal portion reaches the first object to press the second object against the first object.

22. The method of claim 21, wherein in the step of infiltrating the third object with the second object, material of the third object is displaced.

23. The method of claim 21, wherein the third object includes an opening through which a distal portion of the second object is directed to the first object.

24. The method according to claim 18 or 19, wherein the second object comprises a head or bridge which, after re-solidifying the thermoplastic material of the first object, is brought to bear against a proximally facing surface portion of the third object while anchoring a distal portion of the second object in the first object.

25. The method of claim 1, wherein the second object includes a distal face having a plurality of laterally spaced cavities forming the opening and receptive of at least a portion of the flow portion, and pressing the second object against the first object includes pressing the distal face against a proximal face of the first object.

26. The method of claim 25, wherein the second object comprises a plurality of protrusions between the cavities.

27. The method of claim 26, wherein the proximal face of the first object defines a separation plane, wherein after the step of pressing and coupling vibrations into the tool, the protrusion protrudes distally of the separation plane, and the cavity extends inwardly from the separation plane, and a volume of the protrusion is less than or equal to a volume of the cavity.

28. The method of claim 26 or 27, wherein the protrusion comprises an energy directing edge or tip.

29. A method according to claim 26 or 27, wherein the cavities are arranged regularly.

30. The method according to claim 26 or 27, wherein the second object is moved in an axial direction relative to the first object by a penetration depth to penetrate the first object by the step of pressing and coupling vibrations into the tool, and wherein the penetration depth is smaller than a lateral width of the second object.

31. The method of claim 30, wherein the penetration depth is less than a lateral spacing between outermost ones of the cavities.

32. The method of claim 1, comprising pressing a holding device against a proximal face of the first object in the vicinity of the second object while the second object is subjected to pressing and mechanical vibration.

33. The method of claim 1, wherein the second object comprises a mounting structure for mounting another object to the first object, the mounting structure being proximally accessible and belonging to a first portion of the first material, and the second object further comprises a second portion of the second material, wherein a portion of the first portion is embedded in the second material at least after the step of resolidifying the thermoplastic material.

34. The method of claim 33, wherein in the step of pressing and coupling vibration into the tool, the flow portion is caused to flow into a gap between the first and second portions, thereby stabilizing the first portion relative to the second portion.

35. The method of claim 33 or 34, wherein the first portion is metallic and the second portion is plastic.

36. The method according to claim 33 or 34, wherein the second part comprises at least one outer circumferential distal protrusion which is pressed into the first object in the step of pressing and coupling vibrations into the tool.

37. The method according to claim 36, wherein the first and/or second part comprises at least one internal distal protrusion which is pressed into the first object in the step of pressing and coupling vibrations into the tool.

38. The method of claim 1, wherein the engagement structure comprises a series of radial projections and depressions.

39. The method of claim 1, wherein each of the plurality of laterally spaced openings is a distal opening that is laterally spaced from other distal openings of the plurality of laterally spaced openings.

40. A joining element to be secured to a first object comprising a liquefiable thermoplastic material in a solid state in a method according to any one of the preceding claims,

the connector comprises a surface portion having an engagement structure with an undercut and/or being deformable to comprise such an engagement structure with an undercut, whereby the connector can form a form-fitting connection with a first object;

the connector also has a coupling-in structure for being contacted by a tool,

wherein the connector is configured to be pressed to the first object by the tool in physical contact with a coupling-in structure of the connector, while mechanical vibrations are coupled into the tool until the flowing portion of the thermoplastic material of the first object is liquefied and flows into a joining structure, so that after the thermoplastic material has resolidified a form-fitting connection between the first object and the connecting element is produced by the liquefied and resolidified flow portions which are mutually permeable with the joining structure, wherein the engagement structure comprises a plurality of laterally spaced openings that open distally and each define an undercut relative to an axial direction, the flow of the flow portion including flowing back into the plurality of laterally spaced openings and undercuts defined by the plurality of laterally spaced openings, wherein distal portions of a plurality of laterally spaced openings are configured to be embedded in the first object.

41. The connector of claim 40, comprising a first portion of a first material and a second portion of a second material.

42. The connector of claim 41, wherein the first portion is embedded in the material of the second portion and is proximally accessible and includes a mounting structure.

43. The connector of claim 42, where the first portion extends distally to form at least one distal extension.

44. The connector of claim 41, wherein the first material is metal and the second material is plastic.

45. The connector of claim 41, wherein the second material is plastically or elastically deformable.

46. The connector of claim 40, including a distal face having a plurality of laterally spaced cavities forming the opening and capable of receiving at least a portion of the flow portion.

47. The connector of claim 46, including a protrusion between the cavities.

48. The connector of claim 47, including a distal surface portion defining a separation plane, the protrusion having a volume less than or equal to the volume of the cavity relative to the separation plane.